Messages in this thread Patch in this message | | | Subject | [PATCH 1/2] x86, mm: fix gup_pte_range() vs DAX mappings | From | Dan Williams <> | Date | Sat, 25 Feb 2017 09:08:33 -0800 |
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gup_pte_range() fails to check pte_allows_gup() before translating a DAX pte entry, pte_devmap(), to a page. This allows writes to read-only mappings, and bypasses the DAX cacheline dirty tracking due to missed 'mkwrite' faults. The gup_huge_pmd() path and the gup_huge_pud() path correctly check pte_allows_gup() before checking for _devmap() entries.
Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") Cc: <x86@kernel.org> Cc: <stable@vger.kernel.org> Cc: Xiong Zhou <xzhou@redhat.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Thomas Gleixner <tglx@linutronix.de> Reported-by: Dave Hansen <dave.hansen@linux.intel.com> Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- arch/x86/mm/gup.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c index 0d4fb3ebbbac..1680768d392c 100644 --- a/arch/x86/mm/gup.c +++ b/arch/x86/mm/gup.c @@ -120,6 +120,11 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, return 0; } + if (!pte_allows_gup(pte_val(pte), write)) { + pte_unmap(ptep); + return 0; + } + if (pte_devmap(pte)) { pgmap = get_dev_pagemap(pte_pfn(pte), pgmap); if (unlikely(!pgmap)) { @@ -127,8 +132,7 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, pte_unmap(ptep); return 0; } - } else if (!pte_allows_gup(pte_val(pte), write) || - pte_special(pte)) { + } else if (pte_special(pte)) { pte_unmap(ptep); return 0; }
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